Maternal elaborative reminiscing supports preschool children's autobiographical memory, self-concept, and emotion understanding. What are the factors contributing to mothers' elaborative style of reminiscing? In a longitudinal community sample (n = 170 at the final data point), this study explored the role of maternal depression (8–44 months), maternal sensitivity and maternal mind-mindedness (8 months), as well as child factors of joint attention (15 months), attachment security (15 months), and language (26 months) for mother–child reminiscing about a positive (happy) and a negative (scared) event at 44 months. Mothers could be classed into two groups of low versus increasing depression from 8 to 44 months, yet maternal depression did not uniquely predict mother–child reminiscing after accounting for maternal sensitivity and other factors. Instead, maternal sensitivity, children's joint attention, and language uniquely predicted children's elaborations about the scared event at 44 months, and maternal sensitivity uniquely predicted mothers' elaborations about the scared event at 44 months. Mothers who are more sensitive in early interactions may later be better at engaging their children when reminiscing about negative emotions. These findings have implications for the design of interventions targeted at supporting mothers to engage in elaborative reminiscing with their preschool children.